Well a wireless version that monitors temperature and Humidity is what you really want. But you can use one of the remote indoor / outdoor ones that have a wire to a remote probe.

Like this FAQ

http://boards.cannabis.com/showthread.php?t=40868
Zandor Reviewed by Zandor on . quick question? How far/close should my400 hps light be to the tops of me plants ? any help welcome thnx. :) Rating: 5